Github Action: Split Long Command into Multiple Lines

I have a Github action command that is really long:

name: build

on: [push]

jobs:
    build:
        runs-on: ubuntu-18.04
        steps:
            - uses: actions/checkout@v1
            - name: Install Prerequisites
              run: |
                sudo apt-get update
                sudo apt-get install -y --no-install-recommends "a very very long list of prerequisites"

May I know whether it is possible to split the long command into multiple lines for better readability? I have tried the separator '\' but it does not work. Thanks in advance.

Solution 1:

I have a multi line command using backslash to separate the lines as follows:

- name: Configure functions
  run: |
    firebase functions:config:set \
      some.key1="${{ secrets.SOME_KEY_1 }}" \
      some.key2="${{ secrets.SOME_KEY_2 }}" \
    ...    

Note the preceding '|' character.

Solution 2:

You can use the YAML folded style with > which is supported by GitHub Actions.

For example,

run: >
  xvfb-run
  ./mvnw -f my/pom.xml
  clean verify
  -DskipTests

newlines will be replaced with spaces so the above is equivalent to

run: xvfb-run ./mvnw -f my/pom.xml clean verify -DskipTests

Solution 3:

Going to share this in since it has not been mentioned.

You can use:

• | called a Literal Block Scalar which preserves new lines and trailing spaces
• > called a Folded Block Scalar which converts new lines into spaces
• plain old strings, either unquoted, single-quoted or double-quoted

I found the site yaml-multiline.info useful for understanding how yaml strings are interpreted.

For my use case, I ended up doing the following:

run: >-
  for i in $(find . -type f -name "*.log");
  do
   echo "File: ${i} \n";
   cat $i;
   printf '%*s\n' "${COLUMNS:-$(tput cols)}" '' | tr ' ' -;
  done

Solution 4:

This was not possible using backslashes, earlier. See the accepted answer on how to do it now.

As far as I know, GitHub Actions does not support that.

However, you can use environment variables for that.

For example, this script splits your command in 3 lines of code and executes it as one line.

steps:
  - name: Install Prerequisites
    run: |
      sudo apt-get update
      bash -c "$line1 $line2 $line3"
    env:
    - line1='sudo apt-get install -y --no-install-recommends '
    - line2='a very very long list'
    - line3='of prerequisites'

It creates the environment variables line1, line2 and line3 and concats and executes them in a bash session.